Integrated circuits (ICs), such as on-chip radio frequency (RF) ICs employ the use of integrated inductors to perform a range of functions. The inductors are formed on the silicon substrate which is grounded. Typically, the inductors are formed on a dielectric layer formed over the substrate. Inductor coils carrying varying current at high operating frequencies generate magnetic field that penetrates into the substrate below. The magnetic field induces an image current (eddy current) that penetrates into the substrate and flows in the opposite direction as the coil current. The eddy current generates its own field, which opposes the original magnetic field of the inductor. This degrades the quality factor (Q) of the inductor. Additionally, the electric potential difference between the inductor and the grounded silicon substrate creates an electric field across the dielectric layer, pointing towards the substrate. When the coil voltage changes, varying current (displacement current) can flow through the insulating layer to the substrate, causing undesirable power dissipation.
It is therefore desirable to increase quality factor (Q) and reduce power loss of inductors.